这个mysql代码有什么问题

$db_user="root";
$db_host="localhost";
$db_password="root";
$db_name = "fayer";
$conn = mysqli_connect($db_host,$db_user,$db_password,$db_name) or die ("couldn't connect to server");

// perform query
$query = 'SELECT * FROM posts';
$result = mysqli_query($conn, $query) or die ("Couldn't execute query.");

// use returned data
while($row = mysqli_fetch_assoc($result))
{
    echo $row['title'];
}
$db_user="root";
$db_host="localhost";
$db_pass